<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		
		<script type="text/javascript">
			var x;
			console.log(x);//undefined
			
			var m = '3';
			var n = 3;
			if (m == n) {
				console.log('m==n')
			}
			if (m === n) {
				console.log('m===n')
			}
			
			var str = new String('Java AndroidA');
			console.log(str);
			console.log(str.length);
			console.log(str.indexOf('A'));//5
			console.log(str.lastIndexOf('A'));//12
			
			var str2 = 'how are you doing today'
			var array = str2.split(' ');
			console.log(array);
			console.log(array[1]);
			
			if (0) {
				console.log('0')
			}
			if (!0) {
				console.log('!0')
			}
			if ('') {
				console.log('空字符串')
			}
			if ('abc') {
				console.log('abc')
			}
		</script>
	</body>
</html>